Observation of multiple volume reflection of ultrarelativistic protons by a sequence of several bent silicon crystals.

The interactions of 400 GeV protons with different sequences of bent silicon crystals have been investigated at the H8 beam line of the CERN Super Proton Synchrotron. The multiple volume reflection of the proton beam has been studied in detail on a five-crystal reflector measuring an angular beam deflection theta = 52.96 +/- 0.14 microrad. The efficiency was found larger than 80% for an angular acceptance at the reflector entrance of 70 microrad, with a maximal efficiency value of epsilon = 0.90 +/- 0.01 +/- 0.03.

Screening effects in risk studies of thyroid cancer after the Chernobyl accident.

In this article scenarios have been developed, which simulate screening effects in ecological and cohort studies of thyroid cancer incidence among Ukrainians, whose thyroids have been exposed to (131)I in the aftermath of the Chernobyl accident. If possible, the scenarios were based on directly observed data, such as the population size, dose distributions and thyroid cancer cases. Two scenarios were considered where the screening effect on baseline cases is either equal to or larger than that of radiation-related thyroid cancer cases. For ecological studies in settlements with more than ten measurements of the (131)I activity in the human thyroid in May-June 1986, the screening bias appeared small (<19%) for all risk quantities. In the cohort studies, the excess absolute risk per dose was larger by a factor of 4 than in the general population. For an equal screening effect on baseline and radiation-related cancer (Scenario 1) the excess relative risk was about the same as in the general population. However, a differential screening effect (Scenario 2) produced a risk smaller by a factor of 2.5. A comparison with first results of the Ukrainian-US-American cohort study did not give any indication that a differential screening effect has a marked influence on the risk estimates. The differences in the risk estimates from ecological studies and cohort studies were explained by the different screening patterns in the general population and in the much smaller cohort. The present investigations are characterized by dose estimates for many settlements which are very weakly correlated with screening, the confounding variable. The results show that under these conditions ecological studies may provide risk estimates with an acceptable bias.

Volume reflection dependence of 400 GeV/c protons on the bent crystal curvature.

The trend of volume reflection parameters (deflection angle and efficiency) in a bent (110) silicon crystal has been investigated as a function of the crystal curvature with 400 GeV/c protons on the H8 beam line at the CERN Super Proton Synchrotron. This Letter describes the analysis performed at six different curvatures showing that the optimal radius for volume reflection is approximately 10 times greater than the critical radius for channeling. A strong scattering of the beam by the planar potential is also observed for a bend radius close to the critical one.

Volume reflection of a proton beam in a bent crystal.

Volume reflection predicted in the mid-1980s by Taratin and Vorobiev has been observed for the first time in the interactions of a 70 GeV proton beam with a short bent crystal. Incident protons deviate from convex atomic planes in the bulk of the crystal as a result of coherent interaction with bent lattice around the tangency point of particle trajectory with a curved atomic plane. The deflection angle 2theta(R) was found to be (39.5+/-2.0) microrad, or (1.65+/-0.08)theta(c) in terms of the critical angle for channeling. The process has a large probability with respect to channeling and takes place in the angular range equal to the bend angle of atomic planes. It could possibly open new fields of application of crystals in high-energy particle beam optics.

Post-Chernobyl thyroid cancers in Ukraine. Report 2: risk analysis.

On April 26, 1986, the worst nuclear reactor accident to date occurred at the Chornobyl (Chernobyl) power plant in Ukraine. Millions of people in Ukraine, Belarus and Russia were exposed to radioactive nuclides, especially (131)I. Since then, research has been conducted on various subgroups of the exposed population, and it has been demonstrated that the large increase in thyroid cancer is related to the (131)I exposure. However, because of study limitations, quantified risk estimates are limited, and there remains a need for additional information. We conducted an ecological study to investigate the relationship between (131)I thyroid dose and the diagnosis of thyroid cancer in three highly contaminated oblasts in Northern Ukraine. The study population is comprised of 301,907 persons who were between the ages of 1 and 18 at the time of the Chornobyl accident and were living in 1,293 rural settlements in the three study oblasts. Twenty-four percent of the study population had individual thyroid dose estimates and the other 76% had "individualized" estimates of thyroid dose based on direct thyroid measurements taken from a person of the same age and gender living in the same or nearby settlement. Cases include 232 thyroid cancers diagnosed from January 1990 through December 2001, and all were confirmed histologically. Dose-response analyses took into account differences in the rate of ultrasound examinations conducted in the three study oblasts. The estimated excess relative risk per gray was 8.0 (95% CI = 4.6-15) and the excess absolute risk per 10,000 person-year gray was estimated to be 1.5 (95% CI = 1.2-1.9). In broad terms, these estimates are compatible with results of other studies from the contaminated areas, as well as studies of external radiation exposure.

Thyroid cancer among Ukrainians and Belarusians who were children or adolescents at the time of the Chernobyl accident.

Our objective is to assess the regional and temporal dependences of the baseline cases contributing to thyroid cancer incidence among those exposed in childhood or during adolescence in Belarus and Ukraine after the Chernobyl accident. Data are analysed for Kyiv and Sevastopol City and the 25 oblasts (regions) in Ukraine, and for Minsk and Gomel City and the 6 oblasts in Belarus. Average thyroid doses due to the Chernobyl accident were assessed for every birth year in the period from 1968 to 1985. Case data pertain to people who underwent surgical removal of thyroid cancers during the period 1986 to 2001 and who were allocated to their place of residence at the time of the accident. The 35 oblasts/cities were subdivided into an upper, middle and lower group of baseline thyroid cancer incidence. Poisson regressions were performed to estimate age, time and gender dependences of the baseline incidence rates in the three groups. The majority of oblasts/cities with high average doses and the majority of Belarusian oblasts/cities belong to the upper group of baseline thyroid cancer incidence. The baseline in the upper group is estimated to be larger than in the middle group by a factor of 2.3, and by a factor of 4.0 when compared to the lower group. The baseline incidence increases with age and with time since exposure. Estimated baseline incidence rates were found to increase from 1988 to 1999 by factors of three and two for the upper and the two lower groups respectively. The estimated thyroid cancer incidence rates in Belarus and Ukraine, and their dependences on gender and age, are consistent with observed rates found in the larger cancer registries of other countries. In conclusion, the baseline cases are found to contribute about 70% to the thyroid cancer incidence in Ukraine, and about 40% to the incidence in Belarus.

Thyroid cancer risk in areas of Ukraine and Belarus affected by the Chernobyl accident.

The purpose of the present study was to analyze the thyroid cancer incidence risk after the Chernobyl accident and its degree of dependence on time and age. Data were analyzed for 1034 settlements in Ukraine and Belarus, in which more than 10 measurements of the (131)I content in human thyroids had been performed in May/June 1986. Thyroid doses due to the Chernobyl accident were assessed for the birth years 1968-1985 and related to thyroid cancers that were surgically removed during the period 1990-2001. The central estimate for the linear coefficient of the EAR dose response was 2.66 (95% CI: 2.19; 3.13) cases per 10(4) PY-Gy; for the quadratic coefficient, it was -0.145 (95% CI: -0.171; -0.119) cases per 10(4) PY-Gy(2). The EAR was found to be higher for females than for males by a factor of 1.4. It decreased with age at exposure and increased with age attained. The central estimate for the linear coefficient of the ERR dose response was 18.9 (95% CI: 11.1; 26.7) Gy(-1); for the quadratic coefficient, it was -1.03 (95% CI: -1.46; -0.60) Gy(-2). The ERR was found to be smaller for females than for males by a factor of 3.8 and decreased strongly with age at exposure. Both EAR and ERR were higher in the Belarusian settlements than in the Ukrainian settlements. In contrast to ERR, EAR increases with time after exposure. At the end of the observation period, excess risk estimates were found to be close to those observed in a major pooled analysis of seven studies of childhood thyroid cancer after external exposures.

Post-Chornobyl thyroid cancers in Ukraine. Report 1: estimation of thyroid doses.

About 1.8 EBq of 131I was released into the atmosphere during the Chornobyl accident that occurred in Ukraine on April 26, 1986. More than 10% of this activity was deposited on the territory of Ukraine. Beginning 4-5 years after the accident, an increase in the incidence of thyroid cancer among children, believed to be caused in part by exposure to 131I, has been observed in different regions of Ukraine. A three-level system of thyroid dose estimation was developed for the reconstruction of thyroid doses from 131I for the entire population of Ukrainian children aged 1 to 18 at the time of accident: (1) At the first level, individual doses were estimated for the approximately 99,000 children and adolescents with direct measurements of radioactivity in the thyroid (so-called direct thyroid measurements) performed in May-June of 1986; (2) at the second level, group doses by year of age and by gender were estimated for the population of 748 localities (with 208,400 children aged 1-18 in 1986) where direct thyroid measurements of good quality were performed on some of the residents; and (3) at the third level, group doses by age and by gender were estimated for the population of the localities where no thyroid measurements were made in 1986. The third-level doses were then aggregated over the population of each oblast. Data, models and procedures required for each level of thyroid dose estimation are described in the paper. At the first level, individual doses were found to range up to 27,000 mGy, with geometric and arithmetic means of 100 and 300 mGy, respectively. At the second level, group doses were found to be highest for the younger children (aged 1 to 4 years); doses for the older children (aged 16 to 18 years) were 3.5 times smaller. At the third level, average population-weighted doses were found to exceed 35 mGy in the five northern oblasts closer to the Chornobyl reactor site; to be in the 14- to 34-mGy range in seven other oblasts, Kyiv city and Crimea; and to be less than 13 mGy in all other oblasts.

Internal exposure from the ingestion of foods contaminated by 137Cs after the Chernobyl accident--report 2. Ingestion doses of the rural population of Ukraine up to 12 y after the accident (1986-1997).

Doses from the ingestion of 134Cs and 137Cs during 12 y following the Chernobyl accident have been estimated for approximately 3 million persons living in rural areas of the Zhitomir, Rivne, and Kyiv Oblasts of northern Ukraine. This assessment is based upon an extensive monitoring campaign that provided measurements of 137Cs in more than 120,000 samples of milk and in more than 100,000 persons; such measurements were made in approximately 4,500 locations. Two approaches were used for the dose assessment. In the first approach a so-called reference dose is estimated for each settlement on the basis of measured 137Cs concentration in milk, determination of the milk equivalent of diet, and consumption rates; a further assumption is that a high fraction of the food consumed is produced locally. The reference dose is used as the official dose estimate, which is the basis for any decision on possible financial compensation and economic privileges. In a second step, the so-called real age-dependent dose is estimated from the results of whole body counter measurements and the kinetics of radiocesium in the human body. Real doses above 0.5, 5, and 50 mSv were received by about 40%, 10%, and 0.2%, respectively, of the considered population. With the exception of 1986, for which the monitoring results were limited, the real individual doses derived from whole-body counting are consistently lower than the reference doses. However, this difference declined from a factor of 3-4 in 1987-1989 to a factor of approximately 1.5 in the mid 1990's. The difference between reference and real doses is attributed to the effectiveness of countermeasures implemented after the accident. The effectiveness of these countermeasures decreased with time due to increasing economic problems in Ukraine. The collective reference and real doses of the rural population due to the intake of 134Cs and 137Cs are estimated to be 13,300 and 5,300 person-Sv, respectively. Thus, about 8,000 person-Sv is estimated to have been averted by countermeasures.

Internal exposure from the ingestion of foods contaminated by 137Cs after the Chernobyl accident. Report 1. General model: ingestion doses and countermeasure effectiveness for the adults of Rovno Oblast of Ukraine.

The Chernobyl accident, which occurred in April 1986, resulted in the atmospheric release of about 70--100 PBq of 137Cs. This paper examines the doses to the adult population of the northern part of Rovno Oblast, Ukraine, from ingestion of 137Cs. Fallout of 137Cs in these regions was lower than in other regions of Ukraine. However, the transfer of 137Cs from soil to milk in the region considered is high (up to 20 Bq L-1 per kBq m-2) and results in the predominance of internal doses compared to those from external exposure. Numerous measurements of 137Cs soil deposition, 137Cs milk contamination, and 137Cs body burden have been made in the area and form the basis of a general model of internal exposure from the ingestion of foods contaminated by 137Cs. This paper has two main purposes. The first is to develop the general phenomenological description of the process leading to internal exposure from the ingestion of 137Cs contaminated foods in the situation where different countermeasures are realized. The second is to apply the model for the adult population of the northern part of the Rovno Oblast (first report) for the limited time period of up to six years after the accident. The doses actually received by the adults are estimated to be four to eight times smaller than the doses calculated for the situation without countermeasures.

Effective doses due to external irradiation from the Chernobyl accident for different population groups of Ukraine.

A model for the external exposure of the Ukrainian population after the Chernobyl accident was developed. It is based on extensive measurements of external gamma-exposure rates (EGER) in air and of external effective doses of members of five population groups. Questionnaires were used to determine the occupancy times of members of the population groups at three types of locations; inside houses, outdoors, and outside of the home settlement. Behavior factors are defined as the ratio of individual external doses to a reference dose for a phantom standing permanently over an open field with the same average 137Cs activity per unit area as in the settlement. The behavior factors were derived for five population groups (children younger than seven years, the age group from eight to seventeen years, employees, agricultural workers, and pensioners) by two methods: first from direct measurements of individual doses by thermoluminescent dosimetry and an experimental determination of the average 137Cs activity per unit area in the settlement of interest; and second from external gamma-exposure rates in air at various types of locations and from the questionnaire data. The methods were found to be consistent and the results were used to calculate external exposures of the five population groups in the years 1987 through 1991.

[The clinico-tomographic correlates in Alzheimer's disease]. / Kliniko-tomograficheskie korreliatsii pri bolezni Al'tsgeimera.

Brain computed tomographic scans of 43 patients with Alzheimer's disease (moderate and severe dementia) were compared to those of age-matched normal subjects (30 controls). Computed tomographic analysis included some linear and volume ventricular measurements. These indices correlated with relevant psychopathological and psychometric findings. Linear measurements of the ventricular size and the degree of cortical, central atrophy were significantly greater in patients with Alzheimer's disease than in the control group. In line with the disease progression and its development from moderate to severe dementia the degree of brain structural changes increased with the predominance of cortical atrophy in parietal lobes and central atrophy in mediobasal parts of the temporal lobes.

[A genetic analysis of the computed tomographic traits in schizophrenia]. / Geneticheskii analiz komp'iuterno-tomograficheskikh priznakov pri shizofrenii.

The authors analyze clinical and CT evidence obtained on schizophrenic families (42 probands, 70 parents and 23 siblings) versus 162 healthy volunteers. Heritability coefficients were estimated for CT-parameters. Positive and negative psychopathological symptoms and CT-parameters seem to be correlated. It was established that such CT parameters as width of the frontal horn of the left lateral ventricle in the area of nucleus caudatus, width of the central compartment of the left lateral ventricle, width of the frontal horn of the right lateral ventricle in the area of nucleus caudatus, width of the central compartment of the right lateral ventricle may be regarded as markers of predisposition to schizophrenia. The results support the hypothesis on the role of genetic predisposition in the development of neuropathological changes in schizophrenic patients. This may be utilized in medico-genetic consulting and for formulation of the disease prognostic criteria.

[Computerized tomography in the diagnosis of organic brain lesions in patients with schizophrenia]. / Komp'iuternaia tomografiia v diagnostike organicheskoi patologii golovnogo mozga u bol'nykh shizofreniei.

The authors retrospectively analyse CT data obtained in examinations of 1745 patients divided into three groups. Of these, 832 were male and 913 female patients. Group 1 consisted of 721 patients with schizophrenia, group 2 (reference) consisted of 855 mentally normal subjects directed to computer tomographic examination with suspected organic involvement of the brain, and group 3 (control) consisted of 169 mentally and neurologically normal subjects. On the whole the incidence of various organic brain lesions was 8% in group 1, 41.5% in group 2, and 6.5% in control group, whatever the of the examinees or any other factors. Vascular diseases of the nervous system predominated in group 2 as against group 1, being 3.5 times more incident. No intracranial tumors were detected in controls; in schizophrenics computer tomographic signs of volumic brain lesions were detected in 1.5% of cases, being diagnosed more than 10 times more frequently than in group 2 patients.

[Invasive interventions with computerized tomography guidance]. / Invazivnye vmeshatelstva pod kontrolem kompíuternoi tomografii.

Invasive interventions (diagnostic and therapeutic) were conducted on 125 patients. Fifty-six has diseases of the lungs, 16 of the mediastinum, 4 of the pleura, 17 of the liver, 2 of the pancreas, one of the spleen, 15 of the kidneys, 7 of the retroperineal space, two of the soft tissues, and 5 patients had diseases of the skeletal bones. Biopsy was combined with aspiration of the renal cyst content in 7 cases. The diagnostic value of biopsy under control of CT was 86% (106 cases); negative and pseudonegative results were recorded in 18 (14%) patients. The efficacy of biopsy is determined by such factors as the size of the lesion and the depth of its localization in the involved organ, the character of the pathological process and the region of its localization, the site from which the material is collected, and the needles used. Among 7 patients with therapeutic interventions, 5 had good and 2 had satisfactory immediate results. Complications were revealed in 4 (3.3%) patients, pneumothorax was encountered most frequently.

[Cerebral complications in cardiac myxomas]. / Tserebral'nye oslozhneniia pri miksomakh serdtsa.

The authors analyze injuries to the central nervous system in patients with heart myxomas due to tumorous embolism of brain vessels with the development of acute or "delayed" cerebral symptomatology. Stress the difficulty of correct interpretation of acute disorders of cerebral circulation with no other signs of intracavitary heart neoplasm and the possibility of the asymptomatic form of cerebrovascular embolism or its consequences in association with a remarkable clinical picture of heart myxoma. Emphasis is laid on the necessity of carrying out all-round examination of the brain to reveal injuries that may occur under such conditions, to determine the prognosis and treatment policy in the given patients' group, especially in the long-term period after resection of intracavitary heart neoplasm.

[The clinical and computed tomographic criteria of the diagnosis of multiple systemic cerebral atrophy with progressive autonomic insufficiency (the Shy-Drager syndrome)]. / Klinicheskie i komp'iuterno-tomograficheskie kriterii diagnostiki mnozhestvennoi sistemnoi atrofii mozga s progrssiruiushchei vegetativnoi nedostatochnost'iu (sindroma Shaia--Dreidzhera).

Based on clinical and CT examination of 3 patients with Shy-Drager syndrome and the reported data, differential diagnosis of the given diseases is under discussion. Shy-Drager syndrome is characterized by CT signs of progressive atrophy of the pons and cerebellum with no essential changes in the supratentorial brain structures. The authors support a proposal to use the term "multiple systemic atrophy" for designation of the disease entity that includes both Shy-Drager syndrome and sporadic patterns of olivopontocerebellar and strionigral degenerations in which the disease debuts by motor disorders of the extrapyramidal and cerebellar nature rather than by vegetative disturbances.

[Computerized tomography approaches in the study of dementia]. / Kompiuterno-tomograficheskie podkhody v izuchenii dementsii.

Computed tomography was used to study the prevalence rates of various types of intracranial pathology, hydrocephalus (HDC) and cortical atrophy (CA) in patients with late dementia (LD) and to comparatively assess the informative value of tomographic methods of cerebral morphometry. Computed tomographic data were obtained from 432 patients with LD. Despite the type of dementia, the authors revealed intracranial abnormalities of various etiology in 24.5%, postischemic foci being prevalent. Tumors, arachnoidal cysts, and chronic subdural hematomas were more infrequently diagnosed (in 2.6% of cases). HDC and CA were detected in 81.5 and 82.2% of patients with LD, respectively.

Clinico-tomographical aspects in the pathogenesis of vascular dementia.

This article discusses the role of some pathogenetical factors in the main morphological variants of vascular dementia and their correlation with certain clinical parameters. On the basis of computer-tomographical (CT) studies of 62 patients with dementia, it was possible to distinguish three groups of patients, according to the type of parenchymatous brain lesions: (1) 14 patients with "pure" leukoaraiosis (LA); (2) 23 patients with ischemic foci (IF), and (3) 25 patients with a combination of LA and IF. A comparative study of these groups confirmed the concept that in the development of LA and dementia related to it, a special role is being attributed to such factors as arterial hypertension and aging.